JP2016082434A - Waveguide band-rejection filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high power resistance while preventing the unnecessary band, by eliminating generation of microwave discharge, even if a passband and a stop band are close to each other.SOLUTION: In a band-rejection filter provided with a plurality of grooves 8 in the transmission direction of the wide upper and lower surfaces of a rectangular waveguide, the groove 8 in the upper surface and the groove 8 in the lower surface are staggered, and the width dof these grooves 8 in the transmission direction is set wider than the width dof the waveguide 7s surface between the grooves. In this groove 8, its width dis set equal to about 1/4, 3/4 of the guide wavelength of pass frequency band, and the depth dis set about 1/4 of the guide wavelength of blocking frequency band.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a waveguide band stop filter, and more particularly to a structure of a high power resistance filter in which a pass band and a stop band are close to each other.

  FIG. 5 shows a configuration of a corrugated filter used as a conventional band rejection filter. The filter of FIG. 5A is similar to the following Patent Document 1 and has a wide upper and lower surface of the waveguide 1. A groove 2 is provided in the groove 2 and the depth direction of the groove 2 is operated as a resonator. That is, in the blocking (frequency) band, the bottom surface of the upper and lower grooves 2 is a short end where the high-frequency electric field is zero, the vicinity of the waveguide surface is an open end where the electric field is maximum, and the waveguide in the groove 2 is open. A blocking filter is configured.

  The corrugated filter of FIG. 5 (B) is one in which the upper and lower grooves 2 are alternately arranged as shown in the following Patent Document 2. Even in the blocking filter of this structure, the depth direction of the grooves 2 is the same. Unnecessary microwaves can be blocked by using the resonance of.

JP 2007-311838 A JP-A-8-213807 Japanese Patent Laid-Open No. 7-15210

“Microwave Filters, Impedance-matching Networks, and Coupling Structures” George L. Matthaei, Leo Young, E.M.T.Jones (McGraw-Hill)

  By the way, when a magnetron is used for a transmitter of a radar device or the like, unnecessary radiation is often emitted at a frequency slightly higher than the frequency of the transmission wave due to the characteristics of the magnetron. As an example, there is a coaxial magnetron with an output power of 60 kW that operates in the 9.1 GHz band and has unnecessary radiation in the vicinity of 9.5 GHz. In order to suppress this unnecessary radiation, a waveguide type band stop filter is effective.

  However, in the conventional band stop filter, the frequency of about 0.4 GHz is different between the stop band and the pass band, so that the high-frequency electric field strength near the waveguide surface (wide surface) at the edge of the groove 2 increases, Wave discharge may occur. Therefore, it is necessary to take measures against discharge such as pressurizing the inside of the waveguide.

  When the frequency difference between the stop band and the pass band is small, the reason for the high-frequency electric field strength in the vicinity of the waveguide surface at the edge of the groove 2 is as follows. In the conventional corrugated filter, at the stop frequency, the vicinity of the waveguide surface at the edge of the groove 2 has an open end, that is, an electric field maximum. On the other hand, also in the pass frequency, when the stop frequency and the pass frequency are in close proximity, the vicinity of the open end near the waveguide surface at the edge of the groove 2 inevitably increases the electric field. Therefore, the closer the stop frequency and the pass frequency are, the higher the high frequency electric field strength is.

  The present invention has been made in view of the above problems, and its purpose is to eliminate the occurrence of microwave discharge even when the pass band and the stop band are close to each other, while preventing unnecessary bands and high power resistance. Is to provide a waveguide bandstop filter.

  To achieve the above object, the invention according to claim 1 is a band rejection filter in which a plurality of grooves are provided in the transmission direction of the wide upper and lower surfaces of the rectangular waveguide. The grooves are staggered and the width in the transmission direction of these grooves is made wider than the width of the waveguide surface between the grooves, and the width of the groove is set to about n / 4 (n : Odd).

According to the above configuration, for example, in the grooves on the upper surface and the groove on the lower surface that are alternately arranged, the width of the groove is wider than the width of the waveguide surface between the grooves (the waveguide surface without the groove), and It is set to about ¼ of the guide wavelength in the pass frequency band. This increases the distance between the waveguide surfaces between the grooves on the upper surface or the lower surface, and increases the distance between the waveguide surface between the grooves on the upper surface and the waveguide surface between the grooves on the lower surface. Microwave discharge is suppressed due to the withstand power, and good blocking characteristics at a desired frequency can be obtained.
Further, by setting the width of the groove 8 to about n / 4 of the in-tube wavelength of the pass frequency, reflection of the pass frequency by the groove can be reduced.

  According to the waveguide band stop filter of the present invention, even when the pass band and the stop band are close to each other, it is possible to reduce the high-frequency electric field strength at the groove-free portion of the waveguide (wide surface). In addition, there is an effect that the generation of microwave discharge is eliminated and high power resistance can be obtained while preventing unnecessary bands. In addition, a suitable band rejection filter that suppresses unnecessary radiation can be realized by a radar apparatus having a high-power transmitter using a magnetron or the like.

It is side surface sectional drawing which shows the structure of the waveguide band stop filter of the Example which concerns on this invention. It is a perspective view which shows the internal structure of the waveguide band stop filter of an Example. It is a figure which shows the equivalent circuit of the waveguide band stop filter of an Example. It is a graph which shows the attenuation | damping characteristic of the waveguide band stop filter of an Example. It is a perspective view which shows the two structural examples of the conventional waveguide band stop filter.

1 and 2 show a configuration of a waveguide bandstop filter according to an embodiment. This filter is of a corrugated type, in which 5 is an input / output waveguide, 6 is a step waveguide, 7 is a waveguide, and 8 is a groove. In the embodiment, as shown in FIG. 1, wide grooves 8 on the upper surface and grooves 8 on the lower surface are alternately arranged in the transmission direction, and the width d ₁ of the grooves 8 on the upper and lower surfaces is guided between the grooves. It is wider than the width _{d 2} of the tube surface 7s. Furthermore, the width d ₁ of the groove 8 was about 1/4 of the guide wavelength of the pass frequency band, the depth d ₃ of the groove 8 is set to less than about 1/4 of the guide wavelength of the stop band.

For example, when the pass frequency is 9.1 GHz and the stop frequency is 9.5 GHz, the input / output waveguide 5 is a rectangular waveguide having a cross-sectional dimension of 28.5 mm × 12.6 mm. The dimensions of 8 are a width (d ₁ ) of 10 mm and a depth (d ₃ ) of 6 mm, and the width (d ₂ ) of the waveguide surface 7s between the grooves is 4 mm. That is, 10 mm of the width of the groove 8 is about ¼ of the guide wavelength 40.4 mm with a pass frequency of 9.1 GHz, and the depth of 6 mm is ¼ or less of the guide wavelength 7.9 GHz with a guide wavelength of 37.9 mm. It becomes.

Given this configuration the equivalent circuit, since 1/4 or less of the guide wavelength 37.9mm blocking frequency 9.5GHz depth _{d 3} of the groove 8, thereby serially waveguide 7 The entered inductance L is formed, and the waveguide surface 7 s becomes a capacitance C that enters the waveguide 7 in parallel. Therefore, an equivalent circuit of this band rejection filter can be expressed as shown in FIG. The circuit shown in FIG. 3 is a typical low-pass filter, and in the waveguide circuit, the equivalent circuit constant varies depending on the frequency. Therefore, in the embodiment, there is a pass band at a frequency higher than the stop band. However, it operates as a band rejection filter rather than a simple low-pass filter.

According to such a configuration, although the high-frequency electric field of the waveguide surface 7s is high is compared to other portions, longer than the width d ₂ of the waveguide surface 7s width d ₁ of the groove 8, and by arranging the grooves 8 alternating with upper and lower surfaces, vertical and horizontal waveguide surface 7s interval between, that is, the vertical distance d ₄ for spacing d ₁ of the left and right is longer, compared with the conventional corrugated filter The high-frequency electric field strength in that portion can be made relatively small. In the embodiment, it has been confirmed that it normally functions as a band rejection filter with a power of 60 kW without taking measures against discharge such as pressure application of the waveguide.

Further, as described above, the width _{d 2} of the groove 8 and 10 mm, has approximately 1/4 of the guide wavelength 40.4mm pass frequency 9.1GHz, thereby, the reflection by the groove 8 in the pass frequency 9.1GHz It works to be smaller. The step waveguide 6 serves to achieve impedance matching between the filter portion provided with the groove 8 and the input / output waveguide 5.

FIG. 4 shows the attenuation characteristics of the filter of the embodiment. This is the same as the conventional filter shown in FIG. 5A and the filter of the embodiment. The values are the same, the pass frequency is set to 9.1 GHz, the comparison is made with the aim of setting the attenuation to 20 dB at 9.4 GHz, the dotted line 50 is the conventional filter characteristic, and the solid line 51 is the filter characteristic of the embodiment. .
As shown in FIG. 4, in the filter of the embodiment (solid line 51), compared with the conventional filter (dotted line 50), a large attenuation near 9.4 GHz can be obtained, and overall characteristics are good. It has become.

In the embodiment, the grooves 8 are alternately arranged so that one waveguide surface 7 s on the upper and lower surfaces is located at the center of the other groove 8. However, if these grooves 8 are shifted in the transmission direction. The waveguide surface 7 s may be disposed at a position other than the center of the groove 8.
The width d _{2 of the} groove 8 is set to about ¼ of the in-tube wavelength of the pass frequency, but this width d ₂ is about 3/4, 5/4, etc. of the in-tube wavelength of the pass frequency [n / 4 (n: Odd))].

  The band rejection filter of the present invention can be used for a device using a magnetron, an electron tube or the like that radiates unnecessary radiation in the very vicinity of an operating frequency, or a radar device using a transmitter having a large transmission power.

1,7 ... waveguide, 2,8 ... groove,
5 ... Input / output waveguide, 6 ... Step waveguide,
7s: Waveguide surface between grooves.

Claims (1)

A band rejection filter in which a plurality of grooves are provided in the transmission direction of the upper and lower surfaces of the rectangular waveguide,
The upper surface groove and the lower surface groove are shifted from each other, and the width in the transmission direction of these grooves is made wider than the width of the waveguide surface between the grooves, and the width of the groove is set in the pass frequency band. A waveguide band-stop filter characterized in that the wavelength is set to about n / 4 (n: odd number).

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